1. Field of the Invention
The present invention relates generally to the field of ophthalmic, more particularly to intraocular lenses (IOLs), and still more particularly to instruments for implanting IOLs in patient""s eyes.
2. Background Discussion
Consideration of the term xe2x80x9cphakic,xe2x80x9d which refers an eye in which the natural ocular lens is still present, may be helpful to the understanding of the present invention. The term xe2x80x9cphakicxe2x80x9d is in contrast to the term xe2x80x9caphakicxe2x80x9d which refers to an eye from which the natural ocular lens has been removed.
A phakic eye is considered a dynamic or active eye because the existing natural lens is a living part of an eye, and is therefore subject to change over time due to such biological effects as disease or aging. An aphakic eye, on the other hand, is considered a static eye because the natural lens has been removed and thus is no longer subject to biological effects that would otherwise affect the natural lens.
Vision in a phakic eye is caused by light from a viewed object being refracted by the cornea and the natural lens located rearward of the cornea to form an image on the retina at the back of the eye. Such image formation may, for example, be assisted by corrective spectacles, contact lens or corneal reshaping.
A common ocular problem in a phakic eye is impaired vision due to the natural lens becoming cloudy or opaquexe2x80x94a degenerative condition known as xe2x80x9ccataract.xe2x80x9d Cataracts typically form with aging, with most individuals over about 60 years old suffering from cataracts to at least some extent. Cataracts can, however, also occur as a result of trauma, systemic diseases (such as diabetes), ocular diseases, long term steroid therapy, excessive exposure to ultra violet light, and heredity.
So far as is presently known, cataracts cannot be cured, reduced, or even significantly arrested. Corrective treatment for cataracts therefore requires the surgical extraction of the natural lens when the lens becomes so cloudy that vision in the afflicted eye becomes so impaired as to affect the patient""s life style. In this manner a phakic eye becomes an aphakic eye.
After a diseased or defective natural lens has been surgically removed, the typical current vision-restoring treatment is to implant in the aphakic eye a prosthetic lens, called an intraocular lens (IOL), that substitute for the removed natural lens and mimics some of its optical characteristics.
Typical IOLs are constructed having an transparent optic with attached fixation members for maintaining the optical axis of the optic aligned with the optical axis of the eye.
Prior to IOL development (in about the mid-1940""s) thick, high diopter spectacles had to be worn to restore vision in aphakic eyes. However, most patients dislike such spectacles (which may still be needed in some special circumstances in which the implanting of IOLs is not feasible) because of their weight and unattractive appearance.
For a long time, IOLs were typically constructed from a rigid, biocompatible polymethyl methacrylate (PMMA) plastic material. Rigid PMMA IOLs require implanting through relatively large surgical incision in the eye, usually, the same incision required for removing the natural lens in one piece from the eye.
However, with the development in the 1970""s of a phacoemulsification process for ultrasonically breaking up natural lenses to enable their removal through much smaller ocular incisions than had previously been required to remove intact natural lenses. This phacoemulsification process gave immediate rise to the development of small incision, elastically deformable IOLs made of silicone or acrylic. It will be appreciated that small, sutureless ocular incisions, currently as small as about 3.2 to 3.5 mm, surgically made for natural lens extraction and IOL implanting are highly desirable for minimizing trauma to the eye, reducing the possibility of such complications as infection, and speeding patient recovery.
Recently and importantly, in addition to the implanting of IOLs in aphakic eyes to restore vision after removal of the natural lens, there has been considerable interest in developing techniques for implanting IOLs in phakic eyes to correct myopia, hypermetropia, presbyopia and astigmatism associated with non-cataract phakic eyes. Such implanting of corrective IOLs in phakic eyes can obviate the wearing of spectacles or contact lenses, which are troublesome and, in fact, may limit certain activities and professions, or having permanent surgical cornea reshaping, which may not be desired by or feasible for many individuals.
In an aphakic eyes, unless unusual conditions are encountered, IOLs are implanted in the posterior chamber of the eye (i.e., the xe2x80x9cbagxe2x80x9d) from which the natural lens has been removed in order to mimic the natural lens as much as possible. In contrast, corrective IOLs for phakic eyes are desirably implanted in the anterior chamber of the eyes (between the cornea and the iris) because the posterior chamber is still occupied by the natural lens.
Elastically deformable anterior chamber IOLs, to which this present invention indirectly relates, are similar in many respects to current elastically deformable posterior chamber IOLs. However, anterior chamber IOLs are usually much more difficult to implant.
A significant anterior chamber IOL implanting problem relates to the unfolding of elastically deformed IOLs from known IOL inserters into the anterior chamber of the eye, in which the typical axial separation between the cornea and natural crystalline lens is only about 2 mm.
Typical known IOL inserters single fold elastically deformable IOLs in half across the optic, creating what is commonly referred to as a xe2x80x9ctacoxe2x80x9d fold. A xe2x80x9ctacoxe2x80x9d folded IOL requires a space (along the optical axis) equal to one-half the diameter of the optic for the IOL to unfold into. For example, a xe2x80x9ctacoxe2x80x9d folded IOL having a typical optic diameter of 6 mm requires a 3 mm axial space for unfolding. It is thus inevitable that the unfolding of a single folded elastically deformable IOL in the anterior chamber will cause unintentional contact with, and likely injury to, the sensitive posterior endothelial surface of the cornea and/or the anterior surface of the crystalline lens.
A principal objective of the present invention is, thus to provide an IOL insertion instrument that double folds an elastically deformable anterior chamber IOL so that the IOL requires substantially less axial unfolding space in the anterior chamber than does a single folded IOL. Because the double folded IOL having a 6 mm diameter optic requires only about 1.5 mm of anterior chamber axial unfolding space, the possibility of the unfolding optic unintentionally contacting and injuring the endothelial cell surface of the cornea and/or the anterior surface of the crystalline lens is minimized.
In accordance with the present invention, there is provided an instrument for double folding an elastically deformable intraocular lens (IOL) and for inserting said double folded IOL into the anterior chamber of a patient""s eye for controlled unfolding. The instrument comprises an elongate, slender IOL insertion tube having a distal end and a longitudinal axis, an IOL receiving station located in the tube adjacent a cutaway opening in the tube, and a support element configured for holding a central optic region of an IOL received in the IOL receiving station against an inner surface of the tube during double folding of the IOL. Included is an IOL double folding member installed on the tube, the folding member having a converging recess facing the IOL receiving station, the recess being along the tube longitudinal axis and having an IOL discharge opening facing the IOL insertion tube distal end.
Means are included for causing relative axial movement between an IOL received in the IOL receiving station and the IOL double folding member to cause the double folding of the IOL into a general C-shape. A piston is axially slidably disposed in the tube for axially pushing the double folded IOL through the distal end of the tube.
A disposal IOL insertion tip, sized for insertion through an ocular incision no greater than about 3.2 mm, is preferably detachably attached to a distal end of the IOL insertion tube, the insertion tip being flexible and constructed of a silicone or an acrylic material. The insertion tip has an oval cross section having an external width between about two times and three times greater than an external height of the tip. The distal end of the IOL insertion tip is beveled at an angle between about 30 degrees and about 45 degrees to permit gradual and controlled unfolding of the IOL after insertion into an eye.
In accordance with a preferred embodiment of the invention, the IOL folding member is axially movable on said tube and the means for causing relative axial movement between the IOL and the IOL folding member is connected for causing the IOL folding member to move axially along the IOL insertion tube so that the converging recess moves onto the IOL received in the IOL receiving station member, thereby causing the double folding of the IOL received in received IOL receiving station. Further, the means for causing relative movement includes a drive member threadably connected to the tube and in driving engagement with the IOL folding member for causing axial movement thereof.
The support element includes an IOL support member movable between a first position in which the support element permits the insertion of an IOL into the IOL receiving station through the tube cutaway opening and a second position in which the support element holds a central optic region of the IOL against the tube inner surface parallel to said tube longitudinal axis.
Means cooperating with the IOL folding member may be provided for exerting a side pressure on the IOL after being double folded in a general C-shape to thereby compress the double folded IOL into a tighter C-shape.
In a variation instrument, the IOL double folding member is fixed to the IOL insertion tube and the means for causing relative axial movement between an IOL received in the IOL receiving station and the double folding member causes the IOL received in the IOL receiving station to be moved axially through the IOL insertion tube into the converging recess of the IOL double folding member. The means for causing relative axial movement comprises a piston axially slidably disposed in the tube, a distal end of the piston being configured for engaging an edge of an optic portion of an IOL received in the receiving station. In this variation instrument, the support element comprises a slender, axial projection at the piston distal end.
More specifically, in accordance with a preferred embodiment, there is provided the instrument for double folding an elastically deformable intraocular lens (IOL) and for inserting the double folded IOL into the anterior chamber of a patient""s eye for controlled unfolding, comprises an elongate, slender IOL insertion tube having a distal end and a longitudinal axis and an IOL receiving and folding station located inside the tube adjacent a side opening in the tube. The IOL receiving and folding station is configured for receiving an IOL which has an optic and haptics attached to opposing edges of the optic, with the haptics generally aligned with the IOL insertion tube longitudinal axis. Included is an IOL double folding member axially movably mounted on the IOL insertion tube, the IOL double folding member having a converging recess facing the IOL receiving and folding station and an IOL discharge opening facing the distal end of the tube, the recess being along the longitudinal axis of the tube. A driver is threadably installed on an externally threaded element fixed to the IOL insertion tube and is coupled to the IOL double folding member for causing movement of IOL double folding member axially along the IOL insertion tube between a first axial position in which the member is out of engagement with an IOL received in the IOL receiving and folding station and a second axial position in which the member causes the double folding of an IOL received in the station into a general C-shape.
The means for axially moving said IOL folding member between said folding member first and second positions includes an externally threaded member fixed to said IOL insertion tube, said driver being threadably installed on said externally threaded element.
Means are included for axially pushing a double folded IOL positioned in the IOL receiving and folding station through the IOL double folding member discharge opening and the distal end of the tube. An IOL support member having an IOL support element is movable between a first position in which the support element permits the insertion of an IOL into the IOL receiving and folding station through the tube cutaway opening and a second position in which the support element holds a central optic region of the IOL against an inner surface of the tube parallel to the tube longitudinal axis as the IOL is double folded. Preferably, means cooperating with the IOL folding member are included for exerting a side pressure on the IOL after being double folded into a general C-shape to thereby compress the double folded IOL into a tighter C-shape.
Further included are a disposable IOL insertion tip and means for detachably attaching the insertion tip to the IOL insertion tube distal end. The insertion tip has an oval transverse cross sectional shape with an external width that is about 2 to about 3 times greater than an external height, a wide region of the insertion tip being thereby formed; the insertion tip being sized for insertion through an ocular incision no greater than about 3.2 mm. The wide region of the IOL insertion tube distal end is preferably beveled at an angle between about 30 and about 45 degrees
A variation instrument for double folding an elastically deformable intraocular lens (IOL) and for inserting said double folded IOL into the anterior chamber of a patient""s eye for controlled unfolding comprises an elongate, slender IOL insertion tube having a distal end and a longitudinal axis, and IOL receiving station located inside the tube adjacent a side opening in the tube. The IOL receiving station is configured for receiving an IOL, which has an optic and haptics attached to opposing edges of the optic, with the haptics generally aligned with the IOL insertion tube longitudinal axis.
Additionally included is an IOL double folding member fixed to the IOL insertion tube and having a converging IOL engaging recess with a wide opening facing the IOL receiving station and a discharge opening facing the distal end of the IOL insertion tube, the recess being along the tube longitudinal axis. Provided is a support member configured for holding a central optic region of an IOL received in the IOL receiving station against an inner surface of said IOL insertion tube along a line parallel to the insertion tube longitudinal axis. A piston is installed in the IOL insertion tube for axially pushing the IOL received in the IOL receiving station along the tube and into the IOL double folding member converging recess for causing the double folding of the IOL into a general C-shape, and for thereafter pushing the double folded IOL through the distal end of the tube. The support member is formed as an axial projection at the distal end of the piston.
Preferably there are included a disposable IOL insertion tip and means for detachably attaching the insertion tip to the IOL insertion tube distal, the insertion tip having an oval transverse cross sectional shape with an external width that is about 2 to about 3 times greater than an external height, a wide region of the insertion tip being thereby formed, and being sized for insertion through an ocular incision no greater than about 3.2 mm. The wide region of the IOL insertion tube distal end is beveled at an angle between about 30 and about 45 degrees.